1. Field of the Invention
The present invention relates to a method for self-adjusting (autonomously adjusting) the flow of a fluid through a valve or flow control device, and a self adjusting valve or flow control device. This is in particular useful in a production pipe for producing oil and/or gas from a well in an oil and/or gas reservoir, which production pipe includes a lower drainage pipe preferably being divided into at least two sections each including one or more inflow control devices which communicates the geological production formation with the flow space of the drainage pipe.
2. Description of the Background Art
Devices for recovering of oil and gas from long, horizontal and vertical wells are known from US patent publications Nos. 4,821,801, 4,858,691, 4,577,691 and GB patent publication No. 2169018.
These known devices comprise a perforated drainage pipe with, for example, a filter for control of sand around the pipe. A considerable disadvantage with the known devices for oil/and or gas production in highly permeable geological formations is that the pressure in the drainage pipe increases exponentially in the upstream direction as a result of the flow friction in the pipe. Because the differential pressure between the reservoir and the drainage pipe will decrease upstream as a result, the quantity of oil and/or gas flowing from the reservoir into the drainage pipe will decrease correspondingly. The total oil and/or gas produced by this means will therefore be low. With thin oil zones and highly permeable geological formations, there is further a high risk that of coning, i.e. flow of unwanted water or gas into the drainage pipe downstream, where the velocity of the oil flow from the reservoir to the pipe is the greatest.
From World Oil, vol. 212, N. 11 (11/91), pages 73-80, is previously known to divide a drainage pipe into sections with one or more inflow restriction devices such as sliding sleeves or throttling devices. However, this reference is mainly dealing with the use of inflow control to limit the inflow rate for up hole zones and thereby avoid or reduce coning of water and or gas.
WO-A-9208875 describes a horizontal production pipe comprising a plurality of production sections connected by mixing chambers having a larger internal diameter than the production sections. The production sections comprise an external slotted liner which can be considered as performing a filtering action. However, the sequence of sections of different diameter creates flow turbulence and prevents the running of work-over tools.
US 2006/0027377 describes a well conduit that has an aperture for communicating with a target reservoir and a one-way valve in the aperture may be used in injection and production wells. One-way valves are described which use a spring or a ball to control fluid flow in one direction from the interior to the exterior of a pipe.
When extracting oil and/or gas from geological production formations, fluids of different qualities, i.e. oil, gas, water (and sand) is produced in different amounts and mixtures depending on the property or quality of the formation. None of the above-mentioned, known devices are able to distinguish between and control the inflow of oil, gas or water on the basis of their relative composition and/or quality.